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.TH TOUCH 1 "June 13, 2021"
.SH NAME
touch, settime \- change file access and modification times
.SH SYNOPSIS
.nf
\fBtouch\fR [\fB-acm\fR] [\fB-r\fR \fIref_file\fR | \fB-t\fR \fItime\fR | \fB-d\fR \fIdate_time\fR] \fIfile\fR...
.fi

.LP
.nf
\fBtouch\fR [\fB-acm\fR] [\fItime_spec\fR] \fIfile\fR...
.fi

.LP
.nf
\fBsettime\fR [\fB-f\fR \fIref_file\fR] [\fItime_spec\fR] \fIfile\fR...
.fi

.SH DESCRIPTION
The \fBtouch\fR utility sets the access and modification times of each file.
The \fIfile\fR operand is created if it does not already exist.
.sp
.LP
The time used can be specified by \fB-t\fR \fItime\fR, by \fB-d\fR
\fIdate_time\fR, by the corresponding time fields of the file referenced by
\fB-r\fR \fIref_file\fR, or by the \fItime_spec\fR operand. If none of these
are specified, \fBtouch\fR uses the current time.
.sp
.LP
If neither the \fB-a\fR nor \fB-m\fR options are specified, \fBtouch\fR updates
both the modification and access times.
.sp
.LP
A user with write access to a file, but who is not the owner of the file or a
super-user, can change the modification and access times of that file only to
the current time. Attempts to set a specific time with \fBtouch\fR results in
an error.
.sp
.LP
The \fBsettime\fR utility is equivalent to \fBtouch\fR \fB-c\fR
[\fItime_spec\fR] \fIfile\fR.
.SH OPTIONS
The following options are supported in the \fBtouch\fR and \fBsettime\fR
utilities:
.SS "touch"
The following options are supported for the \fBtouch\fR utility:
.sp
.ne 2
.na
\fB\fB-a\fR\fR
.ad
.sp .6
.RS 4n
Changes the access time of \fIfile\fR. Does not change the modification time
unless \fB-m\fR is also specified.
.RE

.sp
.ne 2
.na
\fB\fB-c\fR\fR
.ad
.sp .6
.RS 4n
Does not create a specified \fIfile\fR if it does not exist. Does not write any
diagnostic messages concerning this condition.
.RE

.sp
.ne 2
.na
\fB\fB-d\fR \fIdate_time\fR\fR
.ad
.sp .6
.RS 4n
Uses the specified date_time instead of the current time. The option-argument
must be a string of the form:
.sp
.in +2
.nf
\fIYYYY\fR-\fIMM\fR-\fIDDThh\fR:\fImm\fR:\fISS\fR[.\fIfrac\fR][\fItz\fR]
.fi
.in -2
.sp

or
.sp
.in +2
.nf
\fIYYYY\fR-\fIMM\fR-\fIDDThh\fR:\fImm\fR:\fISS\fR[,\fIfrac\fR][\fItz\fR]
.fi
.in -2
.sp

where
.RS +4
.TP
.ie t \(bu
.el o
\fIYYYY\fR is at least four decimal digits giving the year
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fIMM\fR, \fIDD\fR, \fIhh\fR, \fImm\fR, and \fISS\fR are as with \fB-t\fR
\fItime\fR
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fIT\fR is either the letter \fBT\fR or a single SPACE character
.RE
.RS +4
.TP
.ie t \(bu
.el o
[\fI\&.frac\fR] and [\fI,frac\fR] are either empty, or a period (\fB\&.\fR) or
a comma (\fB,\fR) respectively, followed by one or more decimal digits,
specifying a fractional second
.RE
.RS +4
.TP
.ie t \(bu
.el o
[\fItz\fR] is either empty, signifying local time, or the letter \fBZ\fR,
signifying UTC. If [\fItz\fR] is empty, the resulting time is affected by the
value of the \fBTZ\fR environment variable
.RE
.RE

.sp
.ne 2
.na
\fB\fB-m\fR\fR
.ad
.sp .6
.RS 4n
Changes the modification time of \fIfile\fR. Does not change the access time
unless \fB-a\fR is also specified.
.RE

.sp
.ne 2
.na
\fB\fB-r\fR \fIref_file\fR\fR
.ad
.sp .6
.RS 4n
Uses the corresponding times of the file named by \fIref_file\fR instead of the
current time.
.RE

.sp
.ne 2
.na
\fB\fB-t\fR \fItime\fR\fR
.ad
.sp .6
.RS 4n
Uses the specified \fItime\fR instead of the current time. \fItime\fR is a
decimal number of the form:
.sp
.in +2
.nf
[[\fICC\fR]\fIYY\fR]\fIMMDDhhmm\fR[\fI\&.SS\fR]
.fi
.in -2
.sp

where each two digits represent the following:
.sp
.ne 2
.na
\fB\fIMM\fR\fR
.ad
.sp .6
.RS 4n
The month of the year [01-12].
.RE

.sp
.ne 2
.na
\fB\fIDD\fR\fR
.ad
.sp .6
.RS 4n
The day of the month [01-31].
.RE

.sp
.ne 2
.na
\fB\fIhh\fR\fR
.ad
.sp .6
.RS 4n
The hour of the day [00-23].
.RE

.sp
.ne 2
.na
\fB\fImm\fR\fR
.ad
.sp .6
.RS 4n
The minute of the hour [00-59].
.RE

.sp
.ne 2
.na
\fB\fICC\fR\fR
.ad
.sp .6
.RS 4n
The first two digits of the year.
.RE

.sp
.ne 2
.na
\fB\fIYY\fR\fR
.ad
.sp .6
.RS 4n
The second two digits of the year.
.RE

.sp
.ne 2
.na
\fB\fISS\fR\fR
.ad
.sp .6
.RS 4n
The second of the minute [00-61].
.RE

Both \fICC\fR and \fIYY\fR are optional. If neither is given, the current year
is assumed. If \fIYY\fR is specified, but \fICC\fR is not, \fICC\fR is derived
as follows:
.sp

.sp
.TS
box;
c c
l l .
If YY is:	CC becomes:
_
69-99	19
00-38	20
39-68	ERROR
.TE

The resulting time is affected by the value of the \fBTZ\fR environment
variable. If the resulting time value precedes the Epoch, \fBtouch\fR exits
immediately with an error status. The range of valid times is the Epoch to
January 18, 2038.
.sp
The range for \fISS\fR is [00-61] rather than [00-59] because of leap seconds.
If \fISS\fR is 60 or 61, and the resulting time, as affected by the \fBTZ\fR
environment variable, does not refer to a leap second, the resulting time is
one or two seconds after a time where \fISS\fR is 59. If \fISS\fR is not given,
it is assumed to be 0.
.RE

.SS "settime"
The following option is supported for the \fBsettime\fR utility:
.sp
.ne 2
.na
\fB\fB-f\fR \fIref_file\fR\fR
.ad
.sp .6
.RS 4n
Uses the corresponding times of the file named by \fIref_file\fR instead of the
current time.
.RE

.SH OPERANDS
The following operands are supported for the \fBtouch\fR and \fBsettime\fR
utilities:
.sp
.ne 2
.na
\fB\fIfile\fR\fR
.ad
.sp .6
.RS 4n
A path name of a file whose times are to be modified.
.RE

.sp
.ne 2
.na
\fB\fItime_spec\fR\fR
.ad
.sp .6
.RS 4n
Uses the specified \fItime_spec\fR instead of the current time. This operand is
a decimal number of the form:
.sp
.in +2
.nf
\fIMMDDhhmm\fR[\fIYY\fR]
.fi
.in -2
.sp

where each two digits represent the following:
.sp
.ne 2
.na
\fB\fIMM\fR\fR
.ad
.sp .6
.RS 4n
The month of the year [01-12].
.RE

.sp
.ne 2
.na
\fB\fIDD\fR\fR
.ad
.sp .6
.RS 4n
The day of the month [01-31].
.RE

.sp
.ne 2
.na
\fB\fIhh\fR\fR
.ad
.sp .6
.RS 4n
The hour of the day [00-23].
.RE

.sp
.ne 2
.na
\fB\fImm\fR\fR
.ad
.sp .6
.RS 4n
The minute of the hour [00-59].
.RE

.sp
.ne 2
.na
\fB\fIYY\fR\fR
.ad
.sp .6
.RS 4n
The second two digits of the year.
.sp
\fIYY\fR is optional. If it is omitted, the current year is assumed. If
\fIYY\fR is specified, the year is derived as follows:
.RE

.sp

.sp
.TS
box;
c c
l l .
YY	Corresponding Year
69-99	1969-1999
00-38	2000-2038
39-68	ERROR
.TE

If no \fB-d\fR, \fB-r\fR, or \fB-t\fR option is specified, at least two operands
are specified, and the first operand is an eight- or ten-digit decimal integer,
the first operand is assumed to be a \fItime_spec\fR operand. Otherwise, the
first operand is assumed to be a \fIfile\fR operand.
.RE

.SH USAGE
See \fBlargefile\fR(7) for the description of the behavior of \fBtouch\fR when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
.SH ENVIRONMENT VARIABLES
See \fBenviron\fR(7) for descriptions of the following environment variables
that affect the execution of \fBtouch\fR: \fBLANG\fR, \fBLC_ALL\fR, \fBLANG\fR,
\fBLC_ALL\fR, \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.sp
.ne 2
.na
\fB\fBTZ\fR\fR
.ad
.sp .6
.RS 4n
Determine the timezone to be used for interpreting the \fItime\fR or
\fIdate_time\fR option-argument or the \fItime_spec\fR operand.
.RE

.SH EXIT STATUS
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.sp .6
.RS 4n
The \fBtouch\fR utility executed successfully and all requested changes were
made.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.sp .6
.RS 4n
An error occurred. The \fBtouch\fR utility returned the number of files for
which the times could not be successfully modified.
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.BR futimens (2),
.BR stat (2),
.BR attributes (7),
.BR environ (7),
.BR largefile (7),
.BR standards (7)
.SH NOTES
Users familiar with the BSD environment find that for the \fBtouch\fR utility,
the \fB-f\fR option is accepted but ignored. The \fB-f\fR option is unnecessary
because \fBtouch\fR succeeds for all files owned by the user regardless of the
permissions on the files.
